Simulations have become common in medical education. They can be used for instruction or assessment, and are currently used by many medical schools for end-of-course comprehensive examinations, as well as part of the licensure process in the U.S. and other countries. Because simulations are created explicitly to serve more than one measurement purpose (e.g., selection, placement, diagnosis, monitoring, certification, and program evaluation), the technical attributes needed to optimize or satisfy multiple purposes require rethinking of some of the traditional approaches available in performance measurement research. To meet this need, CRESST researchers conducted a series of workshops on the use of modeling and simulation technologies to assess medical practice and learning. The first workshop focused on the research basis for a psychometrics of medical simulations and the development of methodology for the validation of medical simulations. The second workshop was concerned with related policy issues. And the third workshop focused on certification issues. CRESST produced relevant reports and products that built upon all three workshops. Papers from the first workshop have been published in a supplement to the journal, Military Medicine.